July 27, 2018

Dear Mimecast Shareholder:

I am pleased to invite you to attend the 2018 Annual General Meeting (the “Annual Meeting”) of Mimecast Limited (“Mimecast” or the “Company”) to be held on Thursday, October 4, 2018, at 10:00 a.m. (London time), at Mimecast’s offices located at City Point, One Ropemaker Street, Moorgate, London EC2Y 9AW, United Kingdom.

Details regarding the Annual Meeting and the business to be conducted are more fully described in the accompanying Notice of 2018 Annual General Meeting of the Company and Proxy Statement. We have also enclosed our Annual Report on Form 10-K for the year ended March 31, 2018, which contains, among other things, our audited consolidated financial statements for the year ended March 31, 2018.

Your vote is important. Whether or not you plan to attend the Annual Meeting, I hope you will vote as soon as possible. You may vote by completing your proxy card and mailing it, by telephone or in person at the Annual Meeting. Please review the instructions on the proxy card regarding your voting options.

Thank you for being a Mimecast shareholder. We look forward to seeing you at our Annual Meeting.

Sincerely,

Peter Bauer

Chief Executive Officer

MIMECAST LIMITED

City Point, One Ropemaker Street, Moorgate

London EC2Y 9AW

United Kingdom

NOTICE OF 2018 ANNUAL GENERAL MEETING OF MIMECAST LIMITED

Notice is hereby given that Mimecast Limited (“Mimecast” or the “Company”), will hold its 2018 Annual General Meeting (the “Annual Meeting”) on Thursday, October 4, 2018, at 10:00 a.m. (London time), at Mimecast’s offices located at City Point, One Ropemaker Street, Moorgate, London EC2Y 9AW, United Kingdom, for the purpose of passing the following resolutions:

ORDINARY RESOLUTIONS

Re-election of Directors

Auditors

ADVISORY, NON-BINDING ORDINARY RESOLUTIONS

ADVISORY, NON-BINDING PLURALITY RESOLUTION

Only shareholders of record as of 4:00 p.m. (London time) on October 2, 2018 are entitled to vote at the Annual Meeting as set forth in the Proxy Statement. If you plan to attend the Annual Meeting in person, you should be prepared to present photo identification such as a valid driver’s license or passport and verification of share ownership

for admittance. You are entitled to attend the Annual Meeting only if you were a shareholder as of 4:00 p.m. (London time) on October 2, 2018, or hold a valid proxy for the Annual Meeting. If you are a shareholder of record, your ownership as of the record date will be verified prior to admittance into the meeting. If you are not a shareholder of record but hold ordinary shares through a broker, trustee, or nominee, you must provide proof of beneficial ownership as of the record date, such as an account statement or similar evidence of ownership. Please allow ample time for the admittance process. For instructions on how to vote your ordinary shares, please refer to the section titled “Voting” beginning on page 1 of this Proxy Statement and the explanatory notes set forth in your enclosed proxy card. A copy of this notice can be found at www.mimecast.com and will be available for inspection at the registered office of the Company from the date of this notice until the date of the Annual Meeting and at the Annual Meeting itself.

Shareholders are entitled to appoint a proxy to exercise all or any of their rights to attend and to speak and vote on their behalf at the Annual Meeting. A shareholder may appoint more than one proxy in relation to the Annual Meeting provided that each proxy is appointed to exercise the rights attached to a different share or ordinary shares held by that shareholder. A proxy need not be a shareholder of the Company. The form of proxy, which must be used to make such appointment and give proxy instructions, is included with this Notice of Annual Meeting and Proxy Statement.

By Order of the Board of Directors,

Robert P. Nault

General Counsel and Company Secretary

Company number: 119119

July 27, 2018

Table of Contents

PROXY STATEMENT

FOR THE 2018 ANNUAL GENERAL MEETING OF THE COMPANY

TO BE HELD THURSDAY, OCTOBER 4, 2018

GENERAL INFORMATION

Our Board of Directors (the “Board”) solicits your proxy on our behalf for the 2018 Annual General Meeting (the “Annual Meeting”) of Mimecast Limited and at any postponement or adjournment of the Annual Meeting for the purposes set forth in this Proxy Statement and the accompanying Notice of 2018 Annual General Meeting of Mimecast Limited (the “Notice”). The Annual Meeting will be held at 10:00 a.m. (London time) on Thursday, October 4, 2018, at our offices, located at City Point, One Ropemaker Street, Moorgate, London EC2Y 9AW, United Kingdom. We are mailing this Proxy Statement to shareholders beginning on August 22, 2018.

In this Proxy Statement the terms “Mimecast,” “the Company,” “we,” “us,” and “our” refer to Mimecast. In this Proxy Statement the terms “members”, “shareholders” and “you” refer to the holders of ordinary shares in the capital of the Company. The mailing address of our principal executive offices is Mimecast Limited, City Point, One Ropemaker Street, Moorgate, London EC2Y 9AW, United Kingdom.

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RESOLUTIONS ONE, TWO AND THREE

RE-ELECTION OF DIRECTORS

Our Board of Directors

In accordance with the terms of our Articles of Association, our Board is divided into three classes (each a “Class”), each of which consists, as nearly as possible, of one-third of the total number of directors constituting our entire Board and each of whose members serve for staggered three-year terms. As a result, only one Class of our Board is elected each year. We currently have seven directors. The members of the Classes are divided as follows:

Upon expiration of the term of a Class of directors, directors in that Class are eligible to be elected for a new three-year term at the annual general meeting of shareholders in the year in which their term expires. At the Annual Meeting, Peter Bauer, Jeffrey Lieberman and Hagi Schwartz, whose terms as Class III directors will expire at the Annual Meeting, will stand for election as Class III directors.

During the fiscal year ended March 31, 2018, Geraldine Elliott served on our Board from November 2017 until her resignation in March 2018. Norman Fiore resigned from the Board on January 1, 2018, after serving on the Board since 2009. Bernard Dallė resigned from the Board on April 1, 2017, after serving on the Board since 2009.

The biographies of each of the nominees and continuing directors below contain information regarding each such person’s age as of July 15, 2018, service as a director, business experience, director positions held currently or at any time during the last five years and the experiences, qualifications, attributes or skills that caused the nominating and corporate governance committee to determine that the person should serve as a director of the Company. In addition to the information presented below regarding each such person’s specific experience, qualifications, attributes and skills that led the Board and the nominating and corporate governance committee to the conclusion that he should serve as a director, we also believe that each of our directors has a reputation for integrity, honesty and adherence to high ethical standards. Each of our directors has demonstrated business acumen and an ability to exercise sound judgment, as well as a commitment of service to Mimecast and our Board, in some cases for many years. Finally, we value our directors’ experience in relevant areas of business management and on other boards of directors and board committees.

Our corporate governance guidelines also dictate that a majority of the Board be comprised of independent directors whom the Board has determined are “independent” under the published listing requirements of The Nasdaq Stock Market LLC (“Nasdaq”) and do not have a material relationship with Mimecast that might signal a potential conflict of interest or otherwise interfere with such director’s ability to satisfy his or her responsibilities as an independent director. See “Corporate Governance – Board Independence” below.

There are no family relationships among any of our directors, nominees for director and executive officers.

Nominees

Based on the recommendation of the nominating and corporate governance committee of our Board, our Board has nominated Peter Bauer, Jeffrey Lieberman and Hagi Schwartz for election as directors to serve for a three-year term ending at the 2021 annual general meeting or until their successors are elected and qualified. Each of the nominees is a current member of our Board and has consented to serve if elected.

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Recommendation of the Board

Nominees for Election for a Three-Year Term Ending at the 2021 Annual General Meeting

Peter Bauer, 44, has served as our Chief Executive Officer and a member of our Board since co-founding Mimecast in 2003. Prior to that, Mr. Bauer was a Managing Director at Idion Solutions Pty in Cape Town, South Africa, a software integration and development company that acquired FAB Technology (Pty), a company that he co-founded in 1997. Mr. Bauer holds a diploma in marketing management from the Institute of Marketing Management South Africa. We believe Mr. Bauer is qualified to serve on our Board because of his extensive knowledge and experience as the chief executive officer of our Company, as well as the industry in which we compete.

Jeffrey Lieberman, 44, has served as a member of our Board since September 2012. Mr. Lieberman is currently a Managing Director of the venture capital firm Insight Venture Partners, which he joined in 1998. Prior to joining Insight, Mr. Lieberman was a management consultant at McKinsey & Company, where he focused on strategic and operating issues in the financial services, technology and consumer products industries. Mr. Lieberman currently serves as chairman of the supervisory board of HelloFresh SE (FRA: HFG) (an international meal kit company based in Berlin, Germany). Mr. Lieberman served as a director of Cvent, Inc. (cloud-based event management software and hospitality solutions) from July 2011 through November 2016 and Shutterstock, Inc. (provider of stock photography, stock footage, stock music and editing tools) from June 2007 through December 2016. In addition, Mr. Lieberman currently serves as a director of several private companies. Mr. Lieberman holds a Bachelor of Applied Sciences in systems engineering and a Bachelor of Arts degree in economics from the University of Pennsylvania. We believe Mr. Lieberman is qualified to serve on our Board because of his experience as a seasoned investor in our industry.

Hagi Schwartz, 56, has served as a member of our Board since July 2015. Mr. Schwartz is currently a Venture Partner at Western Technology Investment, which he joined in 2011, and a co-founder at Pretty Simple Solutions Inc. (dba TruEquity) (cloud-based capitalization table management), which he co-founded in July 2010. Mr. Schwartz also co-founded Budgeta Inc. (cloud-based financial analysis) in October 2014 where he currently serves as a member of the board. In 2005, Mr. Schwartz founded Magnolia Capital, an investment advisory firm, where he served as Managing Director until December 2010. Previously, Mr. Schwartz was the Chief Financial Officer of several public and private technology companies including HyperRoll, Inc., ATRICA, Inc., Noosh, Inc., Mercury Interactive and Check Point Software Technologies. Mr. Schwartz served on the board of directors of Silicon Graphics International Corp. (SGI) from August 2004 until December 2015, and was SGI’s audit committee financial expert from the time SGI went public in June of 2005 until December 2015. In addition, Mr. Schwartz has served on the board of directors of BigFix, Inc., TUI University and two other private companies. Mr. Schwartz was the chairman of the audit committee of Collective Inc. and CAN Capital. Mr. Schwartz holds a Bachelor of Arts in Economics and Accounting from Bar Ilan University. We believe Mr. Schwartz is qualified to serve on our Board because of his financial expertise, his significant audit and financial reporting knowledge, his seasoned business perspective and his prior experience as an executive and on boards of other prominent technology companies.

Directors Continuing in Office Until the 2019 Annual General Meeting

Aron Ain, 60, has served as a member of our Board since April 2017. Mr. Ain has served as the Chief Executive Officer and a member of the board of directors of Kronos Incorporated since 2005. He also became the Chairman of the board of directors of Kronos in May 2018 and currently serves on the Kronos compensation committee. Mr. Ain joined Kronos, a leading global provider of workforce management and human capital management cloud solutions, in 1979 and held several leadership roles at the company prior to becoming Chief Executive Officer. He serves on the Board of Trustees of Hamilton College, on the Trustee Advisory Board of Beth Israel

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Deaconess Medical Center, and as Chairman of the Massachusetts High Technology Council. Mr. Ain holds a Bachelor of Arts in economics and government from Hamilton College. He has also participated in a series of executive education programs, including the AEA/Stanford Executive Institute at Stanford University. We believe that Mr. Ain is qualified to serve on our Board because of his extensive experience as chief executive officer of a global software company.

Stephen Ward, 46, has served as a member of our Board since January 2018. Mr. Ward has served as the Chief Information Security Officer at Teachers Insurance and Annuity Association of America (commonly known as TIAA) since May 2013. Previously, from July 2007 through May 2013, he served in a number of executive roles at JPMorgan Chase & Co., serving most recently as the Global Head of Risk and Business Management for Cybersecurity. Prior to joining JPMorgan Chase & Co., Mr. Ward served as a Special Agent in the United States Secret Service focusing on cybersecurity, personal protection and fraud. Mr. Ward holds a Bachelor of Arts degree from Seton Hall University. We believe that Mr. Ward is qualified to serve on our Board because of his extensive management and operational experience in the areas of security and risk management.

Directors Continuing in Office Until the 2020 Annual General Meeting

Christopher FitzGerald, 72, has served as a member of our Board since April 2007. He has served as our lead independent director since our initial public offering in 2015. Mr. FitzGerald served as a non-executive director of City Merchants High Yield Trust, a London based investment company (LON: CMHY), and The Intercare Group, a U.K. pharmaceuticals business. Mr. FitzGerald was also a member of the Committee of Executive Directors and General Counsel at NatWest Group plc. Before that, Mr. FitzGerald was a partner in the London law firm Slaughter and May, where he specialized in advising major financial services businesses. From 2003 to present, Mr. FitzGerald has served as a member of the finance committee of the governing body of Lincoln College, Oxford University. Mr. FitzGerald holds a Master of Arts in Jurisprudence from Oxford University. We believe that Mr. FitzGerald is qualified to serve on our Board because of his extensive business, financial, legal and governance experience, and his long service to our Company.

Neil Murray, 51, has served as our Chief Technology Officer and a member of our Board since co-founding Mimecast in 2003. Prior to that, Mr. Murray served as the Chief Technical Officer of Global Technology Services, a South African provider of business information solutions that acquired Pro Solutions (Prosol Group Pty), a software development company that he co-founded in 1992. We believe Mr. Murray is qualified to serve on our Board because of his extensive knowledge and experience with our Company and its technologies, as well as the industry in which we compete.

Executive Officers

In addition to Mr. Bauer, our Chief Executive Officer, and Mr. Murray, our Chief Technology Officer, who also serve as directors, our executive officers are:

Peter Campbell, 53, has served as our Chief Financial Officer since 2006, and from 2007 to 2015, Mr. Campbell served as a member of our Board. Prior to joining Mimecast, Mr. Campbell served as the Chief Financial Officer of SR Telecom Inc. where he was employed from 2002 to 2006. From 1998 to 2002, Mr. Campbell was an auditor at Ernst & Young in Montreal, Canada. Mr. Campbell is a Chartered Accountant and holds a Bachelor of Commerce and a Graduate Diploma in accounting from the John Molson School of Business, Concordia University, where he also served as a lecturer.

Edward Jennings, 48, has served as our Chief Operating Officer since August 2015. From January 2014 to August 2015, Mr. Jennings was the Chief Marketing Officer of Veracode, Inc., a provider of cloud-based application security, where he also served as Executive Vice President of Sales and Services from February 2012 to December 2013. Prior to that, from February 2011 to January 2012, Mr. Jennings was General Manager at ADP, Inc. (Nasdaq: ADP), a provider of business outsourcing solutions. From August 2008 to December 2010, Mr. Jennings was the Chief Executive Officer of Copanion, Inc., where he also served as Senior Vice

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President of Sales and Marketing from July 2007 to July 2008. Mr. Jennings holds a Master of Business Administration from the Kellogg School of Management, Northwestern University, and a Bachelor of Arts degree from Boston College.

Janet Bishop-Levesque, 51, has served as our Senior Vice President, Systems, Risk and Security, since December 2017. From April 2014 to December 2017 she served as the Chief Information Security Officer of RSA, a Dell Technologies Company, a provider of security technology solutions. Prior to that, from September 2010 to March 2014, Ms. Bishop-Levesque was the Director, Information Security and Regulatory Compliance, at Aspect Software, Inc., a provider of customer contact center software solutions. She also served in a number of senior security and risk roles at Circles, a Sodexo group company, from 2003 to 2010. She serves as a director of the National Cyber Security Alliance and the Advanced Cyber Security Center. Ms. Bishop-Levesque holds a Bachelor of Science degree from the University of Vermont.

Robert P. Nault, 54, has served as our Senior Vice President and General Counsel since September 2016. From May 2014 to May 2016, he served as Senior Vice President, General Counsel and Secretary of Constant Contact, Inc., a provider of email marketing software, where he also served as Vice President, General Counsel and Secretary from March 2007 to May 2014 and as interim Chief Financial Officer from March 2010 to July 2010. Prior to that, Mr. Nault served as Senior Vice President, General Counsel and Secretary of RSA Security Inc., from November 2005 until November 2006 following its acquisition by EMC Corporation in September 2006. Prior to that, Mr. Nault was Vice President and General Counsel of Med-i-Bank, Inc., a provider of software and services for electronic benefit payments, from October 2004 to July 2005; Legal Consultant and Vice President and General Counsel of ON Technology Corporation, an enterprise software company, from 2001 to 2004; and Senior Vice President and General Counsel of The Pioneer Group, Inc., a financial services and alternative investments company, from 1995 to 2000. Before joining Pioneer, Mr. Nault was a member of the corporate department of Hale and Dorr LLP (now Wilmer Cutler Pickering Hale and Dorr LLP). Mr. Nault holds a Bachelor of Arts degree from the University of Rhode Island, and a Juris Doctorate from Boston University School of Law.

Christina Van Houten, 51, has served as our Chief Strategy Officer, since April 2018. Prior to joining Mimecast, from 2014 to March 2018, Ms. Van Houten was Senior Vice President, Marketing Strategy & Product Management, at Infor Global Solutions, an enterprise software company that provides comprehensive business solutions. She served as Vice President, Industry Solution and Strategy, at Infor, from 2011 to 2014. She was Vice President of Strategy and Solutions at IBM Netezza from 2010 to 2011. Prior to that, from 2005 to 2010, she served in senior roles at Oracle Corporation. Ms. Van Houten holds a Master of Business Administration from the Booth School of Business at the University of Chicago, and a Bachelor of Arts degree from Georgetown University.

John J. Walsh, Jr., 53, has served as our Senior Vice President, Engineering, since May 2017. From October 2015 to April 2017, Mr. Walsh served as the Chief Technology Officer of Tremor Video, a provider of video ad platforms. Prior to that, from January 2013 to June 2015, he was the Chief Technology Officer of CareCloud Corporation, a provider of cloud-based practice management, electronic health record, and medical billing software and services. He served as the Senior Vice President, Engineering and Operations, at Constant Contact from 2008 until 2012. Mr. Walsh holds a Master of Business Administration from Boston University, and a Bachelor of Science degree from Rensselaer Polytechnic Institute.

CORPORATE GOVERNANCE

Board Independence

The Board has determined that each of our directors, except for Mr. Bauer as Chief Executive Officer and Mr. Murray as Chief Technology Officer, has no relationship that would interfere with the exercise of

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independent judgment in carrying out the responsibilities of a director and is “independent” within the meaning of our director independence standards and the director independence standards of Nasdaq and the SEC. Furthermore, the Board has determined that each member of each of the committees of the Board is independent within the meaning of Nasdaq’s, the SEC’s, and our applicable committees’ independence standards, including Rule 10A-3(b)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). In making that determination, the Board considered all relevant facts and circumstances, including (but not limited to) the director’s commercial, industrial, banking, consulting, legal, accounting, charitable, and familial relationships. There are no family relationships among any of our directors or executive officers. In addition, a majority of the members of the Board meets the independence standards under the rules of Nasdaq.

Periodically, the Board will evaluate all relationships between us and each director in light of relevant facts and circumstances for the purposes of determining whether a material relationship exists that might signal a potential conflict of interest or otherwise interfere with such director’s ability to satisfy his or her responsibilities as an independent director. Based on this evaluation, the Board will make periodic determinations of whether each director is independent within the meaning of Nasdaq’s, the SEC’s, and our applicable committees’ independence standards.

Code of Business Conduct and Ethics

We have adopted a Code of Business Conduct and Ethics that applies to all of our employees, officers and directors, including our chief executive officer, chief financial officer, controller or principal accounting officer, or other persons performing similar functions. The current version of the Code of Business Conduct and Ethics is available on the Investor Relations/ Corporate Governance section on our website at www.mimecast.com. A copy of the Code of Business Conduct and Ethics may also be obtained, free of charge, upon a request directed to our Chief Compliance Officer at Mimecast Limited, 191 Spring Street, Lexington, Massachusetts 02421 USA, or complianceofficer@mimecast.com. We intend to disclose any amendment or waiver of a provision of the Code of Business Conduct and Ethics that applies to our principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, by posting such information on our website (available at www.mimecast.com) and/or in our public filings with the SEC.

Corporate Governance Guidelines

The Board has adopted corporate governance guidelines to assist and guide its members in the exercise of its responsibilities. These guidelines should be interpreted in accordance with any requirements imposed by applicable Jersey law or regulation, Nasdaq corporate governance listing standards and our Articles of Association. Our corporate governance guidelines are available on the Investor Relations/ Corporate Governance section of our website at www.mimecast.com. Although these corporate governance guidelines have been approved by the Board, it is expected that these guidelines will evolve over time as customary practice and legal requirements change. In particular, those guidelines that encompass legal, regulatory or exchange requirements as they currently exist will be deemed to be modified as and to the extent that such legal, regulatory or exchange requirements are modified. In addition, the guidelines may also be amended by the Board at any time as it deems appropriate.

Board and Committee Meetings

The Board meets on a regularly scheduled basis during the year to review significant developments affecting us and to act on matters requiring their approval. It also holds special meetings when important matters require action between scheduled meetings. Members of senior management regularly attend meetings to report on and discuss their areas of responsibility. During the year ended March 31, 2018, the Board held seven meetings. The Board has three standing committees:

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Three of our incumbent directors attended 100%, and the remaining incumbent directors attended greater than 81%, of all meetings of the Board and meetings of committees of our Board upon which they served (during the periods that they served) during the year ended March 31, 2018. The Board regularly holds executive sessions of the independent directors. Executive sessions do not include employee directors or directors who do not qualify as independent under Nasdaq and SEC rules.

It is our policy that members of our Board are encouraged to attend annual general meetings of our shareholders; however, attendance is not mandatory. Four of the seven directors then in office attended the 2017 annual general meeting.

Committees

Our Articles of Association provide that the Board may delegate any of its powers to committees. The Board has three standing committees: an audit committee, a compensation committee, and a nominating and corporate governance committee. The Board has also adopted a written charter for each of the three standing committees. Each committee charter is available on the Investor Relations/Corporate Governance section of our website at www.mimecast.com.

Audit Committee

Messrs. FitzGerald, Schwartz and Ward currently serve on the audit committee, which is chaired by Mr. Schwartz. The Board has determined that each member of the audit committee is “independent” for audit committee purposes as that term is defined under Rule 10A-3 of the Exchange Act, and the applicable Nasdaq rules. Each member of the audit committee meets the requirements for financial literacy under the applicable rules and regulations of the SEC and Nasdaq. The Board has designated Mr. Schwartz as an “audit committee financial expert,” as defined under the applicable rules of the SEC. The audit committee’s responsibilities include:

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The audit committee met seven times during the year ended March 31, 2018. The audit committee operates under a written charter adopted by the Board, a current copy of which is available at the Investor Relations/Corporate Governance section of our website at www.mimecast.com.

Compensation Committee

Messrs. Ain, FitzGerald and Lieberman currently serve on the compensation committee, which is chaired by Mr. Lieberman. Ms. Elliott joined the compensation committee in November 2017 and replaced Mr. Schwartz, who had previously served on the compensation committee. Mr. FitzGerald joined the compensation committee in April 2018 following Ms. Elliott’s resignation from the Board. The Board has determined that each member of the compensation committee is “independent” as that term is defined in the applicable SEC and Nasdaq rules. The compensation committee’s responsibilities include:

The compensation committee may delegate authority to one or more subcommittees consisting of one or more of its members as it deems appropriate to carry out its responsibilities. The compensation committee met four times during the year ended March 31, 2018. The compensation committee operates under a written charter adopted by the Board, a current copy of which is available on the Investor Relations/Corporate Governance section of our website at www.mimecast.com.

Compensation Committee Interlocks and Insider Participation

During the year ended March 31, 2018, the members of our compensation committee included Messrs. Ain, Lieberman and Schwartz, and Ms. Elliott. Mr. Schwartz and Ms. Elliott resigned from the compensation committee in November 2017 and March 2018, respectively. None of the members of our compensation committee has at any time been one of our officers or employees. None of our executive officers currently serves, or in the past fiscal year has served, as a member of the board of directors or compensation committee of any entity that has one or more executive officers serving on our Board or compensation committee. For a description of transactions between us and members of our compensation committee and affiliates of such members, please see “Certain Relationships and Related Party Transactions.”

Nominating and Corporate Governance Committee

Messrs. Ain, FitzGerald and Lieberman currently serve on the nominating and corporate governance committee, which is chaired by Mr. FitzGerald. The Board has determined that each member of the nominating and corporate governance committee is “independent” as that term is defined in the applicable SEC and Nasdaq rules. The nominating and corporate governance committee’s responsibilities include:

The nominating and corporate governance committee met three times during the year ended March 31, 2018. The nominating and corporate governance committee operates under a written charter adopted by the Board, a current

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copy of which is available on the Investor Relations/Corporate Governance section of our website at www.mimecast.com.

Identifying and Evaluating Director Nominees

The Board has delegated the director selection and nomination process to the nominating and corporate governance committee, with the expectation that other members of the Board, and of management, will be requested to take part in the process as appropriate.

Generally, the nominating and corporate governance committee identifies candidates for director nominees in consultation with management, through the use of search firms or other advisors, through the recommendations submitted by shareholders or through such other methods as the nominating and corporate governance committee deems to be helpful to identify candidates. Once candidates have been identified, the nominating and corporate governance committee confirms that the candidates meet all of the minimum qualifications for director nominees established by the nominating and corporate governance committee. The nominating and corporate governance committee may gather information about the candidates through interviews, detailed questionnaires, comprehensive background checks or any other means that the nominating and corporate governance committee deems to be appropriate in the evaluation process. The nominating and corporate governance committee then meets as a group to discuss and evaluate the qualities and skills of each candidate, both on an individual basis and taking into account the overall composition and needs of the Board. Based on the results of the evaluation process, the nominating and corporate governance committee recommends candidates for the Board’s approval as director nominees for election to the Board. Our nominating and corporate governance committee also has the authority to retain the services of an executive search firm to help identify and evaluate potential director candidates and did so with respect to the candidacy of each of Mr. Ain, who was elected to the Board in April 2017, and Ms. Elliott, who was elected to the Board in November 2017.

Minimum Qualifications

In evaluating proposed director candidates, the nominating and corporate governance committee may consider all facts and circumstances that it deems appropriate or advisable, including, among other things, the skills of the proposed director candidate, his or her depth and breadth of professional experience or other background characteristics, his or her independence, the current size and composition of our Board and the needs of our Board and its respective committees. Some of the qualifications that our nominating and corporate governance committee considers include, without limitation, integrity, judgment, diversity of experience, expertise, business acumen, understanding of our business and industry, potential conflicts of interest and other commitments. Nominees must also have proven achievement and competence in their field and the ability to provide guidance to our management team and make significant contributions to our success, and an understanding of the fiduciary responsibilities that are required of a director. Director candidates must have sufficient time available in the judgment of our nominating and corporate governance committee to perform all Board and committee responsibilities. Members of our Board are expected to prepare for, attend, and participate in all Board and applicable committee meetings.

The charter of our nominating and corporate governance committee includes a specific policy with regard to the consideration of diversity in identifying director nominees, which we believe is essential to have directors representing diversity in many areas, including but not limited to race, ethnicity, gender, age, background, and professional experience. Accordingly, diversity is one of the factors considered by the nominating and corporate governance committee in identifying director nominees.

Shareholder Recommendations

Shareholders may submit recommendations for director candidates to the nominating and corporate governance committee by sending the individual’s name, age, address, current and previous employment dating back five

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fiscal years, and qualifications to Mimecast Limited, 191 Spring Street, Lexington, Massachusetts 02421 USA, Attn: Company Secretary, who will forward all recommendations to the nominating and corporate governance committee. The nominating and corporate governance committee will evaluate any candidates recommended by shareholders against the same criteria and pursuant to the same policies and procedures applicable to the evaluation of candidates proposed by directors or management.

Shareholder Communications

The Board provides to every shareholder the ability to communicate with the Board, as a whole, and with individual directors on the Board through an established process for shareholder communication. For a shareholder communication directed to the Board as a whole, or a shareholder communication directed to an individual director in his or her capacity as a member of the Board, shareholders may send such communication to the attention of the Company’s legal department via U.S. Mail or expedited delivery service to Mimecast Limited, 191 Spring Street, Lexington, Massachusetts 02421 USA, Attn: Legal Department.

Our legal department will review all incoming shareholder communications and, if appropriate, will forward any such communication to each director, and the Chairman of the Board in his or her capacity as a representative of the Board, to whom such communication is addressed, unless there are safety or security concerns that mitigate against further transmission.

Board and Committee Evaluations

The nominating and corporate governance committee oversees the annual Board and committee evaluation process. Generally, the Board and each committee conduct self-evaluations. During the year ended March 31, 2018, the nominating and corporate governance committee met to assess the effectiveness of the Board and the committees. The nominating and corporate governance committee then provided this assessment to the full Board. The nominating and corporate governance committee establishes the Board and committee evaluation process each year and may determine to use an independent third party evaluation process from time to time in the future.

Board Leadership Structure and Board’s Role in Risk Oversight

Mr. Bauer serves as our Chief Executive Officer and as Chairman of the Board. The Board believes that having our Chief Executive Officer as Chairman of the Board facilitates the Board’s decision-making process because Mr. Bauer has first-hand knowledge of our operations and the major issues facing us. This also enables Mr. Bauer to act as the key link between the Board and other members of management.

Our Board has appointed Mr. FitzGerald to serve as our Lead Independent Director. As Lead Independent Director, Mr. FitzGerald presides over meetings of our independent directors, serves as a liaison between the Chairman of the Board and the independent directors and performs such additional duties as our Board may otherwise determine and delegate.

One of the key functions of our Board is informed oversight of our risk management process. Our Board does not have a standing risk management committee, but rather administers this oversight function directly through the Board as a whole, as well as through its standing committees that address risks inherent in their respective areas of oversight. In particular, our Board is responsible for monitoring and assessing strategic risk exposure. Our audit committee is responsible for reviewing and discussing our major financial risk exposures and the steps our management has taken to monitor and control these exposures, including guidelines and policies with respect to risk assessment and risk management. Our audit committee also monitors compliance with legal and regulatory requirements, in addition to oversight of the performance of our external audit function. Our nominating and corporate governance committee monitors the effectiveness of our corporate governance guidelines. Our compensation committee reviews and discusses the risks arising from our compensation philosophy and practices applicable to all employees that are reasonably likely to have a materially adverse effect on us.

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Director Compensation

Members of our Board who are our employees do not receive compensation for their service as directors. The chart below sets forth the annual cash compensation our non-employee directors receive for service on the Board and the committees on which they serve. Messrs. Dallé, Fiore and Lieberman are not considered to be non-employee directors for this purpose and did not receive any compensation under our non-employee director compensation policy.

We pay our non-employee directors quarterly. We also reimburse each non-employee director for out-of-pocket expenses incurred in connection with attending our Board and committee meetings. The compensation committee, with the assistance of our independent compensation consultant, reviews director compensation periodically and recommends changes to the Board as necessary.

Under our non-employee director compensation policy, each new non-employee director receives, at the time of his or her appointment to the Board, an initial, one-time equity grant (the “Initial Grant”) of restricted share units with a grant date fair value equal to $200,000. The Initial Grant vests in equal annual installments over three years, provided, however, that all vesting ceases if the director resigns from the Board or otherwise ceases to serve as a director of the Company, unless the Board determines that the circumstances warrant continuation of vesting. There is a requirement that each non-employee director retain at least 50% of the shares underlying the Initial Grant while the director remains a member of the Board. In addition, on the date of each annual general meeting of shareholders, each continuing non-employee director who has served as a director for the previous six months receives an annual equity grant of restricted share units with a grant date fair value equal to $150,000 that vests in full on the first anniversary of the date of grant, provided, however, that all vesting ceases if the director resigns from the Board or otherwise ceases to serve as a director, unless the Board determines that the circumstances warrant continuation of vesting.

The following table sets forth information regarding compensation earned by each non-employee director who served during the year ended March 31, 2018:

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The following table sets forth the aggregate number of ordinary shares underlying restricted share units held as of March 31, 2018 by each of the persons who served as a non-employee director during the year ended March 31, 2018:

Compensation Risk Assessment

We believe that although a portion of the compensation provided to our executive officers and other employees is performance-based, our executive compensation program does not encourage excessive or unnecessary risk taking. Our compensation programs are designed to encourage our executive officers and other employees to remain focused on both short-term and long-term financial, operational and strategic goals, in particular in connection with our “pay-for-performance” compensation philosophy. As a result, we do not believe that our compensation programs are reasonably likely to have a material adverse effect on us.

Anti-Hedging and Anti-Pledging Policies

Our insider trading policies prohibit all directors, executive officers, and employees from buying our securities on margin, or holding such securities in a margin account and, without prior approval, buying or selling derivatives on such securities, engaging in short sales involving such securities or pledging our securities as collateral for a loan. To date, no such requests have been made or approved.

RESOLUTIONS FOUR AND FIVE

APPROVAL OF THE APPOINTMENT OF OUR INDEPENDENT AUDITOR, AND AUTHORISATION OF THE BOARD TO DETERMINE THE REMUNERATION OF THE AUDITORS

We have appointed Ernst & Young LLP in the United Kingdom as our independent auditor to perform the audit of our consolidated financial statements in Jersey for the fiscal year ending March 31, 2019, and we are asking shareholders to approve this appointment. On a global basis, we have appointed Ernst & Young LLP as our independent registered public accounting firm, for SEC reporting purposes. Ernst & Young LLP has served as our auditors since 2014.

The audit committee annually reviews the auditors’ independence, including reviewing all relationships between the auditors and us and any disclosed relationships or services that may impact the objectivity and independence

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of the auditors, and the auditors’ performance. A majority of the votes properly cast is required in order to appoint Ernst & Young LLP in the United Kingdom as our auditors.

We expect that a representative of Ernst & Young LLP will attend the Annual Meeting and the representative will have an opportunity to make a statement if he or she so chooses. The representative will also be available to respond to appropriate questions from shareholders.

Audit Fees

The following table sets forth the total fees billed by Ernst & Young LLP for audit, audit-related, tax and all other services rendered for the year ended March 31, 2018 and the year ended March 31, 2017:

The audit committee pre-approved all services performed by Ernst & Young LLP for the years ended March 31, 2017 and 2018.

Recommendation of the Board

Pre-Approval Policies for Non-Audit Services

The audit committee has adopted policies and procedures relating to the approval of all audit and non-audit services that are to be performed by our independent registered public accounting firm. These policies generally provide that we will not engage our auditors to render audit or non-audit services unless the service is specifically approved in advance by the audit committee or the engagement is entered into pursuant to the pre-approval procedure described below.

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The audit committee pre-approves all auditing services and the terms of non-audit services, but only to the extent that the non-audit services are not prohibited under applicable law and the committee determines that the non-audit services do not impair the independence of the auditors. In situations where it is impractical to wait until the next regularly scheduled quarterly meeting, the chairman of the audit committee has been delegated authority to approve audit and non-audit services. The chairman is required to report any approvals to the full committee at its next scheduled meeting.

From time to time, the audit committee may pre-approve specified types of services that are expected to be provided to us by our auditors during the next 12 months. Any such pre-approval is detailed as to the particular service or type of services to be provided and is also generally subject to a maximum dollar amount. Any proposed services exceeding pre-approved amounts will also require separate pre-approval by the audit committee.

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RESOLUTION SIX

NON-BINDING, ADVISORY VOTE TO APPROVE RECEIPT OF REPORTS AND ACCOUNTS

As a company organized under the laws of the Bailiwick of Jersey, for each financial year the directors must present a directors’ report, audited accounts and an independent auditors’ report on the financial statements to shareholders at an annual general meeting. Those to be presented at the Annual Meeting are in respect of the year ended March 31, 2018 and will be delivered to the Jersey Companies Registry following the Annual Meeting. The Jersey statutory accounts are substantially similar to the financial statements included in our Annual Report on Form 10-K for the year ended March 31, 2018, which was filed with the SEC on May 29, 2018 and distributed to our shareholders with this Proxy statement. In accordance with our obligations under Jersey law, we will provide our shareholders at the Annual Meeting an opportunity to receive the annual report and ask any relevant and appropriate questions of the representative of Ernst & Young LLP in attendance at the Annual Meeting. The full accounts and reports of Mimecast will be available for inspection prior to and during the Annual Meeting. The vote on this resolution is an advisory vote only, and therefore, not binding on the Company or the Board. However, the Board will consider the voting results when making decisions regarding the future strategy and operations of the Company.

Recommendation of the Board

RESOLUTION SEVEN

NON-BINDING, ADVISORY VOTE TO APPROVE THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS

Section 14A of the Exchange Act requires that we provide our shareholders with the opportunity to vote to approve, on a non-binding, advisory basis, not less frequently than once every three years, the compensation of our named executive officers as disclosed in our annual proxy statement in accordance with the compensation disclosure rules of the SEC.

As described in detail under the heading “Compensation Discussion and Analysis,” we seek to closely align the interests of our named executive officers with the interests of our shareholders. Our compensation programs are designed to reward our named executive officers for the achievement of short-term and long-term financial, operational and strategic goals and the achievement of increased total shareholder return, while at the same time avoiding the encouragement of unnecessary or excessive risk-taking.

Shareholders are urged to read the “Executive Compensation” section of this Proxy Statement, including the “Compensation Discussion and Analysis,” which discusses how our executive compensation policies and procedures implement our compensation philosophy and contains tabular information and narrative discussion about the compensation of our named executive officers. Our Board and the compensation committee believe that these policies and procedures are effective in implementing our compensation philosophy and in achieving our compensation program goals.

The vote on this resolution is not intended to address any specific element of compensation but rather the overall compensation of our named executive officers and the philosophy, policies and practices described in this Proxy Statement. The vote is advisory, which means that the vote is not binding on the Company, our Board or the compensation committee. Although non-binding, the Board and the compensation committee value the opinions

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that shareholders express in their votes and will review the voting results and take them into consideration as they deem appropriate when making future decisions regarding our executive compensation program.

Recommendation of the Board

RESOLUTION EIGHT

NON-BINDING, ADVISORY VOTE ON THE FREQUENCY OF FUTURE ADVISORY VOTES TO APPROVE THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS

Section 14A of the Exchange Act provides that shareholders must be given the opportunity to vote, on a non-binding advisory basis, for their preference as to how frequently we should seek future non-binding advisory votes to approve the compensation of our named executive officers. We are required to solicit shareholder votes on the frequency of future non-binding, advisory votes to approve the compensation of our named executive officers at least once every six years, although we may seek shareholder input more frequently.

By voting with respect to this Resolution Eight, shareholders may indicate whether they would prefer that we conduct future non-binding advisory votes to approve the compensation of our named executive officers every one, two, or three years. Our Board has determined that an annual non-binding advisory vote to approve the compensation of our named executive officers will allow our shareholders to provide timely and direct input on the Company’s executive compensation philosophy, policies and practices as disclosed in the proxy statement each year. The Board believes that an annual vote is therefore consistent with our efforts to engage in an ongoing dialogue with our shareholders on executive compensation and corporate governance matters.

We recognize that the shareholders may have different views as to the best approach for Mimecast, and therefore we look forward to hearing from our shareholders as to their preferences on the frequency of an advisory vote on the compensation of our named executive officers. This vote is advisory and not binding on the Company, the compensation committee or our Board. Although non-binding, the Board and the compensation committee value the opinions that shareholders express in their votes and will review the voting results and take them into consideration when making future decisions regarding the frequency of future advisory votes on the compensation of our named executive officers.

The proxy card provides shareholders with the opportunity to choose among four options (holding the vote every one, two or three years, or abstaining) and, therefore, shareholders will not be voting to approve or disapprove the recommendation of our Board.

Recommendation of the Board

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SECURITY OWNERSHIP OF

CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

The following table sets forth certain information known to us regarding the beneficial ownership of our ordinary shares as of June 30, 2018, for:

Beneficial ownership is determined in accordance with the rules of the SEC and generally includes voting or investment power with respect to securities. Except as noted by footnote, and subject to community property laws where applicable, we believe, based on the information provided to us, that the persons and entities named in the table below have sole voting and investment power with respect to all ordinary shares shown as beneficially owned by them.

The table lists applicable percentage ownership based on 59,599,656 ordinary shares outstanding as of June 30, 2018, unless indicated otherwise. Options to purchase ordinary shares that are exercisable, and ordinary shares that may be acquired upon the vesting of restricted share units, in each case, within 60 days of June 30, 2018, are deemed to be beneficially owned by the persons holding these options or restricted share units, as applicable, for the purpose of computing percentage ownership of that person, but are not treated as outstanding for the purpose of computing any other person’s ownership percentage. Unless otherwise indicated, the address for each beneficial owner is c/o Mimecast Limited, CityPoint, One Ropemaker Street, Moorgate, London EC2Y 9AW, United Kingdom.

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Section 16(a) Beneficial Ownership Reporting Compliance

Section 16(a) of the Exchange Act requires our directors and executive officers and persons who own more than 10% of our ordinary shares, to file with the SEC initial reports of beneficial ownership and reports of changes in beneficial ownership. Officers, directors and greater than 10% shareholders are required by SEC regulations to furnish us with copies of all such reports.

We were a foreign private issuer under SEC rules until April 1, 2018. By virtue of our status as a foreign private issuer for the year ended March 31, 2018, our executive officers, directors and persons who beneficially own more than 10% of our ordinary shares were not required to file Section 16 reports of their beneficial ownership or changes in beneficial ownership prior to April 1, 2018.

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EXECUTIVE COMPENSATION

Compensation Discussion and Analysis

Overview

This Compensation Discussion and Analysis describes the Company’s executive compensation program as it relates to the following “named executive officers”:

The following discussion should be read together with the compensation tables and related disclosures set forth below.

Our Company

We are a leading global provider of cloud cyber resilience solutions for corporate data and email. Email is the number-one threat vector. Our fully-integrated, pure cloud services protect customers across the globe from incidents that typically start with email, including advanced cyberattacks, data loss, downtime, and human error. We mitigate the significant business disruption caused by email failure and downtime. Our cloud archive secures, stores and manages data, while addressing compliance, regulatory and e-discovery requirements, and improving employee productivity.

We serve approximately 30,400 customers and protect millions of their employees around the world. Our service scales effectively to meet the needs of customers of all sizes. We sell our services through direct sales efforts and through our channel partners. Our sales model is designed to meet the needs of small and mid-market organizations and large enterprises across a wide range of industries and in over 130 countries. We have approximately 1,200 employees in twelve offices in the United States, the United Kingdom, South Africa, Australia, Dubai, UAE, the Netherlands and Germany.

Effective April 1, 2018, we began filing periodic reports and registration statements with the SEC as a U.S. domestic issuer, after we determined that, as of September 30, 2017, we no longer qualified as a foreign private issuer under SEC rules. As a U.S. domestic issuer, we must now, for the first time, make our SEC filings under the rules applicable to U.S. domestic issuers, and must include certain disclosures that were not previously required, including this Compensation Discussion and Analysis.

Executive Compensation – Summary

The key objectives of our executive compensation program are:

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We expect to continue to provide our executive officers with a significant portion of their compensation through cash incentive compensation contingent upon the achievement of financial and operational metrics as well as through equity compensation. These two elements of executive compensation are aligned with the interests of our shareholders because the amount of compensation ultimately received will vary with our financial and operational performance. Equity compensation derives its value from the appreciation of our ordinary shares, which in the future is likely to fluctuate based on our financial and operating performance. Historically, all of our equity compensation for our executive officers has been in the form of options to purchase our ordinary shares, which only have intrinsic value if our share price increases over time.

Performance Highlights

Our performance in year ended March 31, 2018 was very strong. Our key financial measures, GAAP revenue and Adjusted EBITDA (calculated as set forth below under the heading “Executive Compensation Program Elements – Incentive Compensation – Performance Metrics, Goals and Actual Performance”), also grew, with revenue rising from $186.6 million in the prior year to $261.9 million in fiscal 2018, a growth rate of over 40%, and Adjusted EBITDA increasing from $11.8 million to $25.8 million, a growth rate of 118%. In addition, our total shareholder return (“TSR”) for fiscal 2018 was 58%.

Our strong short-term performance, however, is also backed up by our equally strong long-term performance. For example, over the past three years, our TSR has grown over 250%, while our revenue has increased nearly 85%.

The first chart below reflects the Company’s three-year TSR versus the three-year TSR of the other companies in the Company’s compensation peer group. See “Compensation Peer Group” below. The second chart compares the three-year total compensation of our Chief Executive Officer (“CEO”) (as set forth in the “2018 Summary Compensation Table” below) and the three-year indexed TSR.

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Corporate Governance Highlights

The compensation committee regularly reviews best practices in executive compensation and uses the guidelines below to design our compensation programs.

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Recent Changes to Our Compensation Program

To strengthen the alignment of the compensation program with the evolving strategic objectives of our Company, the compensation committee adopted several notable changes to the compensation program in the past two years. These changes include:

Compensation Setting Process

Our Board, the compensation committee and our CEO are all involved in our executive compensation decision-making process. The compensation committee considers a broad range of quantitative and qualitative factors to assess the overall performance of the Company and its executives, including advice from the compensation committee’s independent compensation consultant and input from our CEO (with respect to the compensation of the named executive officers other than himself). After consulting with the independent compensation consultant and the CEO, the compensation committee determines the compensation of all executive officers of the Company other than the CEO. The compensation committee provides its recommendation on CEO compensation to the full Board for approval.

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When setting executive compensation, our compensation committee and Board consider, among other things, our overall company performance, individual performance of the named executive officer, and compensation paid to executive officers in our peer group.

Roles, Responsibilities and Process

Our compensation committee, which is comprised entirely of independent directors, reviews the compensation packages for our named executive officers, including an analysis of all elements of compensation separately and in the aggregate. Our compensation committee operates under a written charter adopted by our Board, which provides that the compensation committee has overall responsibility for:

In reviewing and approving these matters, our compensation committee considers such matters as it deems appropriate, including our financial and operating performance, the alignment of the interests of our executive officers and our shareholders, and our ability to attract and retain qualified and committed individuals. In determining the appropriate compensation levels for our CEO, the compensation committee meets outside the presence of all our executive officers. With respect to the compensation levels of all other executive officers, the compensation committee meets outside the presence of all executive officers except our CEO. Our CEO annually reviews the performance of each of the other named executive officers with the compensation committee. The compensation committee believes that it has established an executive compensation program that is appropriate for our Company, with consideration given to our current growth stage, industry practices, and investor sentiment. Our executive compensation program will continue to evolve as our Company matures and as corporate governance and executive compensation best practices change over time.

Independent Compensation Consultant

The compensation committee has retained the services of Radford, an Aon company, as independent executive compensation consultant, to advise the compensation committee on compensation matters related to the executive officer and director compensation programs. In the year ended March 31, 2018, Radford assisted the compensation committee with, among other things:

Radford reported to the compensation committee and had direct access to the chairman and the other members of the compensation committee. Beyond advice related to the executive and director compensation programs, Radford did not provide other services to the Company in fiscal 2018.

The compensation committee determined that Radford’s work for the compensation committee did not raise any conflicts of interest. Radford’s work has conformed to the independence factors and guidance provided by the Dodd-Frank Wall Street Reform and Consumer Protection Act, the SEC and Nasdaq.

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Compensation Peer Group

The compensation committee and management have worked with Radford to identify and select a peer group of companies as a reference group to provide a broad perspective on competitive pay levels and practices. Peer companies were selected based on the following criteria:

For the year ended March 31, 2018, the Company’s peer group, as approved by the compensation committee, consisted of the following 20 companies:

The compensation committee does not directly tie any pay elements to particular benchmarks within the peer group. Instead, the peer data is used as a market-check analysis and is just one factor considered in the annual compensation approval process. Other important considerations include employee knowledge, skills and experience; individual performance; internal pay equity; scope of responsibilities; and any retention concerns.

Executive Compensation Program Elements

The primary elements of our executive compensation program are:

The compensation committee takes a comprehensive view of all compensation components, which allows us also to make compensation determinations that reflect the principles of our compensation philosophy. We strive to achieve an appropriate mix between the various elements of our compensation program to meet our compensation objectives and philosophy. Our compensation committee, however, does not apply any rigid allocation formula in setting our executive compensation, and may make adjustments to this approach for various positions after giving due consideration to prevailing circumstances, the individuals involved and their responsibilities, experience and performance.

Base Salary

We provide base salary to our named executive officers to compensate them for services rendered on a day-to-day basis. Base salary also provides guaranteed cash compensation to secure the services of our executive talent. We believe that providing a competitive base salary relative to the companies with which we compete for executive talent is a necessary element of a compensation program that is designed to attract and retain talented and experienced executives. We also believe that attractive base salaries can motivate and reward our executive officers for their overall performance.

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Base salaries for our named executive officers are annually reviewed by the compensation committee with Radford. Base salaries are adjusted when it is determined necessary; however, this may not necessarily be on an annual basis. Salaries may be adjusted by the compensation committee after the review of the following items:

The table below shows the annual base salaries for our named executive officers for the year ended March 31, 2017, compared to the year ended March 31, 2018:

Incentive Compensation

For the year ended March 31, 2018, the compensation committee established a cash incentive bonus plan (the “Incentive Plan”) for our executives, which provided for quarterly cash incentive bonus payments. The cash incentive bonuses are focused on the short-term and are intended to compensate our executives for the achievement of corporate performance targets. The corporate performance targets are designed to conform to financial metrics contained in the budget developed by our management and reviewed and approved by the Board. The target amounts payable under the Incentive Plan are calculated as a percentage of the applicable executive’s base salary.

The compensation committee approves the corporate performance targets and the formula for determining potential bonus amounts based on achievement of those targets. The compensation committee works with the CEO, the Chief Financial Officer and the Chief Human Resources Officer to identify corporate performance targets generally based on the board-approved budget. The corporate performance targets typically represent stretch goals that are generally designed to be difficult to fully achieve. The compensation committee believes that establishing targets in this way incents executives to overachieve. As a result, the compensation committee generally does not expect that all of the targets will be fully achieved in all periods. As such, executive bonuses can be highly variable from year to year and are not guaranteed.

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We strongly believe that cash incentives based on corporate performance serve to align the interests of our executives with the interests of our shareholders because they focus executive attention on important metrics aligned with our long-term strategic goals aimed to drive the growth of long-term, sustainable shareholder value. Bonus payments under the Incentive Plan are capped at 200% of target.

Payout Opportunities and Earned Awards

The table below shows the target award under the Incentive Plan for the year ended March 31, 2018 as a percentage of each named executive officer’s annual base salary and the total of all quarterly cash bonus payments made to our named executive officers for performance in the year ended March 31, 2018. Quarterly performance is reviewed and the corresponding payments are approved by the compensation committee and made following the end of each fiscal quarter. The details regarding the determination of these cash bonus awards are discussed below.

Performance Metrics, Goals and Actual Performance

For the year ended March 31, 2018, our Incentive Plan bonus was based on two corporate performance metrics: (1) revenue and (2) Adjusted EBITDA. Revenue was weighted at 80% and Adjusted EBITDA was weighted at 20%. Revenue is consolidated revenue calculated in accordance with generally accepted accounting principles in the United States (“GAAP”), except that the effects of changes in foreign currency exchange rates are excluded from the calculation to better reflect the actual performance of our Company and the direct efforts of our executive officers. While management estimates the impact of foreign currency exchange rates in the budgeting process, the compensation committee believes that the effect of actual foreign exchange rate movements should not have a positive or negative impact on executive incentive compensation. Adjusted EBITDA is a non-GAAP financial measure that we define as net (loss) income, adjusted to exclude: depreciation, amortization, disposals and impairments of long-lived assets, share-based compensation expense, restructuring expense, interest income and interest expense, provision for income taxes and foreign exchange (expense) income and includes rent paid in the period related to locations that are accounted for as build-to-suit facilities. Similar to revenue, Adjusted EBITDA is revised to account for the effects of changes in foreign currency exchange rates. Adjusted EBITDA is also further revised to reflect certain software amortization costs. For a reconciliation of these non-GAAP financial measures to the nearest comparable GAAP measure, please see Appendix A.

For each metric, executives could earn 20% of the weighted target payout for achievement of threshold performance, 100% of target for target performance, and a maximum of 200% of target for meeting or exceeding

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our maximum stretch goal. The chart below reflects the payout scale for Incentive Plan bonuses based on various levels of achievement.

Payouts are determined using linear interpolation between the percentages stated above. Quarterly payments are capped at 100% with any overachievement earned to be reconciled at the end of the fiscal year based on actual achievement.

The following chart sets forth for each performance metric, on a quarterly basis, the target, the achievement, the achievement percentage and the payout percentage.

Equity Incentives

Long-term incentive compensation in the form of equity awards is an integral part of our overall executive compensation program. Providing our named executive officers with the opportunity to realize value through share ownership is a powerful tool to attract and retain highly qualified executives, achieve strong long-term share price performance and align our executive officers’ interests with those of our shareholders. In addition, the vesting features of our equity awards contribute to executive retention.

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To determine the size of annual equity grants, our compensation committee generally considers prior executive performance, role and responsibility, the executive’s ability to influence the Company’s long-term growth and business performance, among other factors. Additionally, the compensation committee takes into consideration equity grants at approximately the 50th percentile of our peer group.

In past years, we have typically granted options to our executive officers. Our compensation committee continues to believe that options are inherently performance-based, requiring share price appreciation before there is any real value earned, while remaining a simple and transparent incentive vehicle. However, for fiscal year 2019, our compensation committee determined that annual equity grants should include a mix of options and restricted share units, which can add a strong retention element to the overall compensation mix while limiting dilution.

Historically, the compensation committee has granted equity awards to executives in February of each year. For the year ended March 31, 2018, the compensation committee, however, determined to align the grant date for executive equity awards with the grant date for other eligible employees receiving annual equity awards, which is April 1^st. As a result, we did not grant any equity awards to our named executive officers in the year ended March 31, 2018, other than an option grant to Ms. Bishop-Levesque to purchase 80,000 ordinary shares in connection with the commencement of her employment with the Company in December 2017. Ms. Bishop-Levesque’s grant was intended to induce her to join the Company and to compensate her for equity forfeited when she left her prior employer. All executive officers, however, received equity awards in the early part of the year ending March 31, 2019.

In connection with the executive equity grant that occurred in April 2018 (fiscal year 2019), the compensation committee sought to generally achieve a balance between share options and restricted share units based on value as follows: 75% of the value relates to share options and 25% of the value relates to restricted share units. Value for this purpose is based on an assumed share price appreciation over the vesting period of the awards. The compensation committee also recognized that the desire to achieve this balance may be outweighed by other compensation considerations. For the share options, 25% of the award vests on the first anniversary of the grant date, while the remaining award vests in equal quarterly installments over the next three years. The restricted share units vest in equal annual installments over four years from the grant date. The equity awards granted to the named executive officers in the year ending March 31, 2019 to date are set forth in the table below.

Benefits and Perquisites

For the year ended March 31, 2018, we provided our named executive officers with the same benefits that are provided to all employees generally, including medical, dental and vision benefits, group term life and long-term disability insurance and participation in our 401(k) plan.

Severance and Related Benefits

We have entered into employment agreements or offer letters with each of our named executive officers that provide for specified payments and benefits in connection with a change in control or termination of employment under certain circumstances. Our goal in providing these severance and change in control payments and benefits is to offer sufficient continuity protection such that our named executive officers will focus their full time and attention on the requirements of the business rather than the potential implications for their respective positions. We have also determined that accelerated vesting provisions with respect to outstanding equity awards in connection with a

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change in control or a qualifying termination of employment following a change in control are appropriate because they encourage our named executive officers to stay focused on the business in those circumstances, rather than focusing on the potential implications for them personally. The employment agreements and offer letters are described in more detail below under the heading “Employment Arrangements with our Named Executive Officers.”

Pension Benefits

We did not sponsor any defined benefit pension or other actuarial plan for our named executive officers during the year ended March 31, 2018.

Nonqualified Deferred Compensation

We did not maintain any nonqualified defined contribution or other deferred compensation plans or arrangements for our named executive officers during the year ended March 31, 2018.

Additional Compensation Policies and Practices

Compensation Risk Oversight

Our compensation committee has responsibility for establishing our compensation philosophy and objectives, determining the structure, components, and other elements of our compensation programs, and reviewing and approving the compensation of our named executive officers. In addition, our executive compensation programs and decisions have, as one of their objectives, to reduce incentives to expose the Company to imprudent risks that might harm the Company or our shareholders. Our compensation committee has overseen the establishment of a number of governors and controls that address compensation-related risk and serve to mitigate such risk. As a result, the compensation committee has concluded that the Company’s compensation policies and practices are not reasonably likely to have a material adverse effect on our Company.

Anti-Hedging and Pledging Policies

Under our insider trading policy, employees are prohibited from buying or selling puts, calls, other derivative securities of the Company or any derivative securities that provide the economic equivalent of ownership of any of the Company’s securities or an opportunity (direct or indirect) to profit from any change in the value of the Company’s securities, except with the pre-approval from the General Counsel. Furthermore, the Company’s employees may not use the Company’s securities as collateral in a margin account or pledge Company securities as collateral for a loan (or modify an existing pledge), except with pre-approval from the General Counsel

Tax

We have not provided or agreed to provide any of our executive officers with a gross-up or other reimbursement for tax amounts they might pay pursuant to Section 4999 or Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”), or otherwise. Sections 280G and 4999 of the Code provide that executive officers, directors who hold significant shareholder interests and certain other service providers could be subject to significant additional taxes if they receive payments or benefits in connection with a change in control of our Company that exceed certain limits, and that we or our successor could lose a deduction on the amounts subject to the additional tax. Section 409A also imposes additional significant taxes on the individual in the event that an employee, director or service provider receives “deferred compensation” that does not meet the requirements of Section 409A.

Generally, Section 162(m) of the Code disallows a federal income tax deduction for public company compensation in excess of $1 million paid for any fiscal year to “covered employees” of the company. With

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respect to taxable years before January 1, 2018, compensation in excess of $1 million was exempt from this deduction limit if it qualified as “performance-based compensation” within the meaning of Section 162(m) and was payable pursuant to a binding written agreement in effect on November 2, 2017. The compensation committee has endeavored to structure compensation to maintain deductibility under Section 162(m) of the Code to the extent practicable, while maintaining the ability to provide a competitive compensation program for our named executive officers.

Recently-enacted tax legislation, effective for taxable years beginning after December 31, 2017, (1) expands the scope of Section 162(m) such that all named executive officers are “covered employees” and anyone who was a named executive officer in any year after 2016 will remain a covered employee for as long as he or she (or his or her beneficiaries) receive compensation from the Company and (2) eliminates the exception to the deduction limit for commission-based compensation and performance-based compensation, except with respect to certain grandfathered arrangements in effect as of November 2, 2017 that are not subsequently materially modified. Accordingly, compensation paid to our named executive officers in excess of $1 million will not be deductible unless it qualifies for the transition relief applicable to certain arrangements in place as of November 2, 2017, as described above.

The compensation committee believes that shareholder interests are best served if the committee retains maximum flexibility to design executive compensation programs that meet stated business objectives. For these reasons, the compensation committee, while considering tax deductibility as a factor in determining executive compensation, may not limit such compensation to those levels that will be deductible, particularly in light of the recent expansion of the covered employee group and the elimination of the exception for performance-based compensation.

2018 Summary Compensation Table

The following table provides information regarding the compensation paid, earned, and received by each of our named executive officers for the fiscal years indicated.

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2018 Grants of Plan-Based Awards Table

The following table shows information regarding grants of plan-based awards during the fiscal year ended March 31, 2018 to our named executive officers.

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Outstanding Equity Awards at March 31, 2018 Table

The following table sets forth certain information regarding outstanding equity awards granted to our named executive officers that remained outstanding as of March 31, 2018. Options to purchase our ordinary shares granted prior to November 2015 were granted pursuant to the Mimecast 2010 EMI Share Option Scheme and options granted after such date were granted pursuant to the Mimecast Limited 2015 Share Option and Incentive Plan.

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2018 Option Exercises and Stock Vested Table

The following table shows information regarding options exercised during the year ended March 31, 2018. None of our named executive officers had share awards vest in the year ended March 31, 2018.

Pension Benefits

None of our named executive officers participates in or has account balances in qualified or non-qualified defined benefit plans sponsored by us.

Non-Qualified Deferred Compensation

None of our named executive officers participates in or has account balances in non-qualified defined contribution plans or other deferred compensation plans maintained by us.

Employment Arrangements with our Named Executive Officers

We have entered into employment agreements or offer letters with each of our named executive officers that provide for specified payments and benefits in connection with a change in control or a termination of employment under certain circumstances. Our goal in providing these severance and change in control payments and benefits is to offer sufficient continuity protection such that our named executive officers will focus their full time and attention on the requirements of the business rather than the potential implications for their respective positions. We have also determined that accelerated vesting provisions with respect to outstanding equity awards in connection with a change in control or a qualifying termination of employment following a change in control are appropriate because they encourage our named executive officers, to stay focused on the business in those circumstances, rather than focusing on the potential implications for them personally.

Our named executive officers are bound by confidentiality and non-disclosure provisions. None of our named executive officers is entitled to a tax gross-up payment, whether pursuant to the terms of their employment agreement or offer letter, or otherwise.

Peter Bauer

Pursuant to the employment agreement with Mr. Bauer, he serves as our Chief Executive Officer on an at-will basis and as a director. Mr. Bauer currently receives a base salary of $349,600, which is subject to periodic review and adjustment. Mr. Bauer is also eligible for an annual performance bonus targeted at 80% of his base salary and to participate in the employee benefit plans generally available to employees, subject to the terms of those plans.

The employment agreement further provides that if Mr. Bauer’s employment is terminated due to his death, he will be entitled to a pro-rated portion of his annual target bonus to the extent not already paid. If Mr. Bauer’s

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employment is terminated by us without cause (as defined in the employment agreement) or Mr. Bauer terminates his employment with us for good reason (as defined in the employment agreement), he will be entitled to receive: (i) continued payment of his base salary for a period of six months, plus two weeks for every year of employment completed with the Company up to a maximum of 12 months (such period, the “Severance Period”) and (ii) if Mr. Bauer is participating in the Company’s group health plan immediately prior to the date of termination and elects COBRA health continuation, a monthly cash payment in an amount equal to the employer portion of his monthly health insurance premium until the earlier of the end of the Severance Period or the end of Mr. Bauer’s COBRA health continuation period. In lieu of the severance payments and benefits set forth in the preceding sentence, in the event Mr. Bauer’s employment is terminated by us without cause or he terminates his employment with us for good reason, in either case within 12 months following a change in control (as defined in the employment agreement), he is entitled to receive (i) an amount equal to (A) his current annual base salary plus (B) his target annual cash incentive compensation for the year of termination, (ii) if Mr. Bauer is participating in the Company’s group health plan immediately prior to the date of termination and elects COBRA health continuation, a monthly cash payment in an amount equal to the employer portion of his monthly health insurance premium until the earlier of 12 months following the date of termination and the expiration of his continuation coverage under COBRA, and (iii) accelerated vesting of all share options and other share-based awards held by Mr. Bauer as of the date of termination. Receipt of the severance payments and benefits described above is conditioned upon Mr. Bauer entering into an effective separation agreement, containing, among other provisions, a general release of claims against the Company and our affiliates, confidentiality, return of property and non-disparagement. In addition, pursuant to the terms of the employment agreement, upon a change in control, 50% of the unvested portion of all share options and other share-based awards held by Mr. Bauer shall immediately accelerate and vest.

Mr. Bauer’s employment agreement also contains non-competition and non-solicitation provisions that apply during his employment and for one year thereafter.

Peter Campbell

Pursuant to the employment agreement with Mr. Campbell, he serves as our Chief Financial Officer on an at-will basis. Mr. Campbell currently receives a base salary of $360,800, which is subject to periodic review and adjustment. Mr. Campbell is also eligible for an annual performance bonus targeted at 60% of his base salary and to participate in the employee benefit plans generally available to employees, subject to the terms of those plans.

The agreement further provides that if Mr. Campbell’s employment is terminated due to his death, he will be entitled to pro-rated portion of his bonus for the year of termination to the extent not already paid. If Mr. Campbell’s employment is terminated due to his disability, we are required to provide Mr. Campbell four months’ written notice during which time he will continue to earn his salary and bonus. In the event that Mr. Campbell’s employment is terminated by us for any reason other than cause (as defined in the employment agreement), death or disability, we are required to give Mr. Campbell (i) four months written notice or, in lieu thereof, continuation of his base salary and Company-paid medical and dental benefits for such period, (ii) a pro-rata bonus for the year of termination, and (iii) base salary continuation and continuation of Company-paid medical and dental benefits for six months following termination (which shall be inclusive of payments and benefits provided pursuant to clause (i) above). In the event that Mr. Campbell terminates his employment with us for any reason, he must provide us with 120 days’ notice, which we may waive provided that we continue to pay him his base salary for such period. In such event, he will also be entitled to a pro-rated bonus for the year of termination to the extent not already paid. In the event of a change in control (as defined in the employment agreement), 50% of the unvested portion of all time-based share options and other share-based awards held by Mr. Campbell shall immediately accelerate and vest. In addition, in the event that within one year following a change in control, Mr. Campbell’s employment is terminated by the Company without cause or Mr. Campbell terminates his employment for good reason (as defined in the employment agreement), subject to execution and effectiveness of a general release of claims in favor of the Company, all unvested time-based share options and other share-based awards held by Mr. Campbell will immediately accelerate and vest.

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Mr. Campbell’s employment agreement contains non-competition and non-solicitation provisions that apply during his employment and for six months thereafter.

Edward Jennings

Pursuant to the offer letter with Mr. Jennings, he serves as our Chief Operating Officer on an at-will basis. Mr. Jennings currently receives a base salary of $331,500, which is subject to periodic review and adjustment. Mr. Jennings is also eligible for an annual performance bonus targeted at 90% of his base salary and to participate in the employee benefit plans generally available to employees, subject to the terms of those plans.

The offer letter further provides that in the event Mr. Jennings’ employment is terminated for any reason other than for cause (as defined in the offer letter), he will be entitled to six months of base salary and medical benefit continuation. Receipt of such severance payments and benefits is conditioned upon Mr. Jennings entering into a general release of claims in favor of the Company and our affiliates. In the event of a change in control (as defined in the offer letter), 50% of the unvested portion of all share options held by Mr. Jennings shall immediately accelerate and vest. In addition, in the event that, within one year following a change in control, Mr. Jennings’ employment is terminated by the Company without cause or Mr. Jennings is required to assume a position with materially different job duties or responsibilities, his base salary or total on target compensation is reduced by more than 5% or there is a change in the location of his employment of more than 50 miles (unless such relocation is within 50 miles of his then-current residence), all unvested share options held by Mr. Jennings will immediately accelerate and vest.

Mr. Jennings has signed our standard agreement, which includes non-competition and non-solicitation provisions that apply during his employment and for one year thereafter.

Robert P. Nault

Pursuant to the offer letter with Mr. Nault, he serves as our Senior Vice President and General Counsel on an at-will basis. Mr. Nault currently receives a base salary of $331,800, which is subject to periodic review and adjustment. Mr. Nault is also eligible for an annual performance bonus targeted at 50% of his base salary and to participate in the employee benefit plans generally available to employees, subject to the terms of those plans.

The offer letter further provides that, in the event that Mr. Nault’s employment is terminated by the Company without cause (as defined in the offer letter) or Mr. Nault terminates his employment for good reason (as defined in the offer letter), he will be entitled to continuation of base salary and health and dental insurance for nine months following termination as well as an amount equal to his target bonus. Receipt of such severance payments and benefits is conditioned upon Mr. Nault entering into a general release of claims in favor of the Company and our affiliates. In the event of a change in control (as defined in the offer letter), 50% of the unvested portion of all share options and other share-based awards held by Mr. Nault shall immediately accelerate and vest. In addition, in the event that within one year following a change in control, Mr. Nault’s employment is terminated by the Company without cause or Mr. Nault terminates his employment for good reason, all unvested share options and other share-based awards held by Mr. Nault will immediately accelerate and vest.

Mr. Nault has signed our standard agreement, which includes non-competition and non-solicitation provisions that apply during his employment and for one year thereafter.

Janet Bishop-Levesque

Pursuant to the offer letter with Ms. Bishop-Levesque, she serves as our Senior Vice President, Systems Risk and Security, on an at-will basis. Ms. Bishop-Levesque currently receives a base salary of $275,000, which is subject to periodic review and adjustment. Ms. Bishop-Levesque is also eligible for an annual performance bonus targeted at 50% of her base salary and to participate in the employee benefit plans generally available to employees, subject to the terms of those plans.

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The offer letter further provides that, in the event that Ms. Bishop-Levesque’s employment is terminated by the Company without cause (as defined in the offer letter) or Ms. Bishop-Levesque terminates her employment for good reason (as defined in the offer letter), she will be entitled to continuation of base salary and health and dental insurance for six months following termination as well as an amount equal to her target bonus. Receipt of such severance payments and benefits is conditioned upon Ms. Bishop-Levesque entering into a general release of claims in favor of the Company and our affiliates. In the event of a change in control (as defined in the offer letter), 50% of the unvested portion of all share options and other share-based awards held by Ms. Bishop-Levesque shall immediately accelerate and vest. In addition, in the event that, within one year following a change in control, Ms. Bishop-Levesque’s employment is terminated by the Company without cause or Ms. Bishop-Levesque terminates her employment for good reason, all unvested share options and other share-based awards held by Ms. Bishop-Levesque will immediately accelerate and vest.

Ms. Bishop-Levesque has signed our standard agreement, which includes non-competition and non-solicitation provisions that apply during her employment and for one year thereafter.

Estimated Payment and Benefits Upon Termination or Change of Control

The following tables set forth the estimated payments and benefits our named executive officers would receive pursuant to the terms of the named executive officer’s employment agreement or offer letter upon a qualifying termination of employment or change in control assuming such event occurred on March 31, 2018.

Peter Bauer

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Peter Campbell

Edward Jennings

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Robert P. Nault

Janet Bishop-Levesque

Rule 10b5-l Sales Plans

Our directors and executive officers may adopt written plans, known as Rule 10b5-l plans, in which they will contract with a broker to buy or sell ordinary shares on a periodic basis. Under a Rule 10b5-l plan, a broker executes trades pursuant to parameters established by the director or executive officer when entering into the plan, without further direction from them. Any Rule 10b5-l Plan adopted by a director or officer must comply with the requirements of Rule 10b5-l under the Exchange Act and our insider trading policy. The director or executive officer may amend or terminate the plan in some circumstances. Our directors and executive officers may also buy or sell additional ordinary shares outside of a Rule 10b5-l plan, provided they are in compliance with our insider trading policy, which includes not being in possession of material, nonpublic information about our Company.

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Equity Compensation Plans

In accordance with SEC rules, the following table provides information, as of March 31, 2018, about the securities authorized for issuance under our equity compensation plans.

Equity Compensation Plan Information

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RELATED PARTY TRANSACTIONS

Certain Relationships and Related Party Transactions

Other than compensation arrangements for our directors and named executive officers, which are described elsewhere in this Proxy Statement, below we describe transactions since April 1, 2017 to which we were a party or will be a party, in which:

We believe that all of these transactions were on terms as favorable as could have been obtained from unrelated third parties.

Registration Rights

As of June 30, 2018, the holders of an aggregate of 16,372,828 ordinary shares, or their permitted transferees, are entitled to rights with respect to the registration of these shares under the Securities Act. These rights are provided under the terms of a Registration Rights Agreement between us and the holders of these shares, which was entered into in connection with our convertible preference share financings, and include demand registration rights, short-form registration rights and piggyback registration rights.

Demand Registration Rights

Under the terms of the Registration Rights Agreement, we will be required, upon the written request of the holders of a majority of the shares that are entitled to rights under the Registration Rights Agreement, held by former holders of Series A preferred shares, Series B preferred shares and founder shares, including entities affiliated with Insight Venture Partners, to register all or a portion of these shares for public resale as soon as reasonably practicable within 60 days of such request. We are not required to effect a registration pursuant to this provision of the Registration Rights Agreement (i) during the period 60 days before our good faith estimate of a date of filing of, and ending 180 days after the effective date of, a registration initiated by us; (ii) after we have effected one registration pursuant to this provision of the Registration Rights Agreement at the request of former holders of Series A preferred shares or founder shares; (iii) after we have effected two registration statements pursuant to this provision of the Registration Rights Agreement at the request of former holders of Series B preferred shares; or (iv) if the initiating holders propose to dispose of securities that may be registered on Form S-3 or Form F-3. If such a registration is to be an underwritten offering, then the holders’ registration rights are conditioned upon such holders’ participation in such underwriting. We may defer the filing of a registration statement once during any twelve-month period for a period of not more than 120 days, if we provide a certificate signed by our chief executive officer stating that, in the good faith judgment of our Board, it would be materially detrimental to us and our shareholders for such registration statement to be filed at that time.

Short-Form Registration Rights

If we are eligible to file a registration statement on Form S-3 or Form F-3 and have not effected more than two such registrations within the preceding twelve-month period, these holders have the right, upon written notice to us of more than 10% of the shares entitled to rights under the Registration Rights Agreement held by former holders of Series A preferred shares, Series B preferred shares, or founder shares, including Insight Venture Partners, to have such shares registered by us as soon as reasonably practicable within 45 days of such request, if the proposed aggregate price of the shares to be registered by the holders requesting registration is at least $5.0 million. However, we may defer the filing of a registration statement once during any twelve-month period

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for a period of not more than 120 days, if we provide a certificate signed by our chief executive officer stating that, in the good faith judgment of our Board, it would be materially detrimental to us and our shareholders for such registration statement to be filed at that time.

Piggyback Registration Rights

If we register any of our securities for our own account, the holders of these shares are entitled to include their shares in the registration. If such registration is to be an underwritten offering, then the holders’ registration rights are conditioned on such holders’ participation in such underwriting.

Other Obligations

The registration rights are subject to certain conditions and limitations, including the right of the underwriters of an offering to limit the number of ordinary shares to be included in the registrations. We are generally required to bear the expense of all registrations, except underwriting discounts and commissions. The Registration Rights Agreement also contains the mutual commitment of us and the holders to indemnify each other for losses attributable to untrue statements or omission of a material fact or violations of the Securities Act or state securities laws incurred by us with registrations under the agreement.

Termination

The registration rights and our obligations thereunder terminate on November 18, 2022, which is seven years after the closing of our initial public offering, or, as to any individual holder, at such earlier time at which all shares held by such holder can be sold in any three-month period without registration in compliance with Rule 144 of the Securities Act.

Registration Statement on Form F-3

We have a filed a Registration Statement on Form F-3, commonly referred to as a “shelf registration,” that permits us to sell in a registered offering up to $50 million of our securities at our discretion. In addition, the registration statement also covers the registration of 20,539,000 ordinary shares held by our existing shareholders, which includes the ordinary shares covered by the Registration Rights Agreement described above. These shareholders could affect their rights under the Registration Rights Agreement by requiring that we initiate an offering under the registration statement. The shelf registration statement was declared effective by the SEC on March 14, 2017.

Other Arrangements

We were previously party to an arrangement with Dawn Capital, pursuant to which we paid Dawn Capital an amount of £12,000 per annum for the services of Norman Fiore as a member of our Board. During the year ended March 31, 2018, we paid Dawn Capital £9,000 under this arrangement, which was terminated in January 2018 upon Mr. Fiore’s resignation from the Board.

Limitation of Liability and Indemnification of Officers and Directors

We have entered into indemnification agreements with each of our directors and executive officers. These indemnification agreements require us, among other things, to indemnify our directors and executive officers against liabilities that may arise by reason of their status or service. These indemnification agreements also require us to advance all expenses incurred by the directors and executive officers in investigating or defending any such action, suit or proceeding. The indemnity’s granted to directors are subject to certain limitations imposed by Jersey law. We believe that these agreements are necessary to attract and retain qualified individuals to serve as directors and executive officers.

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Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers or persons controlling the registrant pursuant to the foregoing provisions, we have been informed that, in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable.

The limitation of liability and indemnification provisions included in our indemnification agreements that we entered into or may in the future enter into with our directors and executive officers may discourage shareholders from bringing a lawsuit against our directors and executive officers for breach of their fiduciary duties. They may also reduce the likelihood of derivative litigation against our directors and executive officers, even though an action, if successful, might benefit us and other shareholders. Further, a shareholder’s investment may be harmed to the extent that we pay the costs of settlement and damage awards against directors and executive officers as required by these indemnification provisions. At present, we are not aware of any pending litigation or proceeding involving any person who is or was one of our directors, officers, employees or other agents or is or was serving at our request as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, for which indemnification is sought, and we are not aware of any threatened litigation that may result in claims for indemnification.

We have obtained insurance policies under which, subject to the limitations of the policies, coverage is provided to our directors and executive officers against loss arising from claims made by reason of breach of fiduciary duty or other wrongful acts as a director or executive officer, including claims relating to public securities matters, and to us with respect to payments that may be made by us to these directors and executive officers pursuant to our indemnification obligations or otherwise as a matter of law.

Certain of our non-employee directors may, through their relationships with their employers, be insured and/or indemnified against certain liabilities incurred in their capacity as members of our Board.

Other Transactions with Our Executive Officers and Directors and Affiliated Entities

We have granted share options and restricted share units to our executive officers and certain of our directors. See the section captioned “Executive Compensation – Outstanding Equity Awards at March 31, 2018 Table” for a description of these equity awards.

Policies and Procedures for Related Party Transactions

The audit committee of our Board has the primary responsibility for reviewing and approving or disapproving “related party transactions,” which are transactions between us and related persons in which the aggregate amount involved exceeds or may be expected to exceed $120,000 and in which a related person has or will have a direct or indirect material interest. For this purpose, a related person is defined as a director, executive officer, nominee for director or greater than 5% beneficial owner of our ordinary shares, in each case since the beginning of the most recently completed year, and their immediate family members. Our audit committee charter provides that the audit committee shall review and approve or disapprove any related party transactions. The audit committee will review these transactions under our Code of Business Conduct and Ethics, which governs conflicts of interests, among other matters, and is applicable to our employees, officers and directors.

All of the transactions described above were entered into prior to the adoption of this policy. Accordingly, each was approved by disinterested members of our Board after making a determination that the transaction was executed on terms no less favorable than those that could have been obtained from an unrelated third party.

TRANSACTION OF OTHER BUSINESS

The Board knows of no other matters that will be presented for consideration at the Annual Meeting. If any other matters are properly brought before the Annual Meeting, the persons appointed in the accompanying proxy will

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be entitled to vote the ordinary shares represented thereby in accordance with their best judgment on such matters, under applicable laws.

SHAREHOLDER PROPOSALS

Procedures for Submitting Shareholder Proposals

Requirements for Shareholder Proposals to be Brought Before the Annual General Meeting. Our Articles of Association provide an advance notice procedure for shareholders to nominate director candidates for election, including proposed nominations of persons for election to the Board. Only persons nominated by, or at the direction of, our Board or by a shareholder who has given proper and timely notice to us prior to the meeting, will be eligible for election as a director. For notice to be timely, it must be received at our registered office not less than 90 nor more than 120 calendar days prior to the first anniversary of the previous year’s annual meeting (or if the date of the annual meeting is advanced more than 30 calendar days or delayed by more than 60 calendar days from such anniversary date, not earlier than the 120th calendar day nor more than 90 days prior to such meeting or the 10th calendar day after public announcement of the date of such meeting is first made). These advance notice provisions may have the effect of precluding the conduct of certain business at a meeting if the proper procedures are not followed or may discourage or deter a potential acquirer from conducting a solicitation of proxies to elect its own slate of directors or otherwise attempt to obtain control of us.

Requirements for Shareholder Proposals to be Considered for Inclusion in the Company’s Proxy Materials. In addition to the requirements stated above, any shareholder who wishes to submit a proposal for inclusion in our proxy materials must comply with Rule 14a-8 promulgated under the Exchange Act. For such proposals to be included in our proxy materials relating to our annual meeting of shareholders in 2019, all applicable requirements of Rule 14a-8 must be satisfied and we must receive such proposals no later than April 24, 2019. Such proposals must be delivered to our Company Secretary at Mimecast Limited, 191 Spring Street, Lexington, Massachusetts 02421 USA, Attn: Company Secretary.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any reports, statements, or other information that we file at the SEC’s public reference room at the following location: 100 F Street, N.E., Washington, D.C. 20549.

Please call the SEC at 1-800-732-0330 for further information on the public reference room. The Company’s SEC filings are also available to the public from commercial document retrieval services and at the website maintained by the SEC at www.sec.gov. You may also read and copy any document we file with the SEC on the Investor Relations/Reports and Filings section of our website at www.mimecast.com.

We will provide without charge to each person to whom a copy of the proxy statement is delivered, upon the written or oral request of any such persons, additional copies of our Annual Report on Form 10-K for the year ended March 31, 2018 as filed with the SEC. Requests for such copies should be addressed to Mimecast Limited, 191 Spring Street, Lexington, Massachusetts 02421 USA, Attn: Robert Sanders, IR Contact, or email us at Investors@mimecast.com or call us at (800) 614-4530.

You should rely on the information contained in this document to vote your ordinary shares at the Annual Meeting. We have not authorized anyone to provide you with information that is different from what is contained in this document. This document is dated July 27, 2018. You should not assume that the information contained in this document is accurate as of any date other than that date, and the mailing of this document to shareholders at any time after that date does not create an implication to the contrary. This Proxy Statement does not constitute a solicitation of a proxy in any jurisdiction where, or to or from any person to whom, it is unlawful to make such proxy solicitations in such jurisdiction.

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Appendix A

Reconciliation of Non-GAAP Financial Measures

REPORTED RESULTS VARIATION FROM EXECUTIVE COMPENSATION TARGET ACHIEVEMENT FISCAL 2018